Additive for lubricants



2,754,269 ADDITIVE FUR LUBRICANTS Jones I. Wasson, Union, and Louis A. Mikeska, Westfield,

N. 3., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application December 1, 1953, Serial No. 395,615- 7 Claims. (Cl. 25255) The present invention relates to an improved lubricant additive and the process of making the same. It relates particularly to an anti-wear and rust inhibiting agent obtained by the oxidation of highly refined petroleum oils of naphthenic nature.

Certain machine elements, such as the hypoid gears used in automotive vehicles, may be subjected at times to extremely heavy pressures of the order of hundreds of thousands of pounds per square inch. Under these conditions the film of lubricating oil separating various metal parts is likely to fail, so that the surfaces contact each other directly with resultant seizure or excessive wear and early failure. To combat this deficiency in lubricating oils, a group of compounds known as extreme pressure agents has been developed. These additives contain active sulphur, phosphorus, chlorine or a combination of these elements which react with the metal surfaces at the high temperatures generated by friction at extremely high pressures. The presence of additives of this nature in lubricating oils causes corrosive action on the metal parts lubricated so that the use of special corrosion inhibitors is required. For this reason, the employment of extreme pressure additives is to be confined to cases of a special nature.

A wide intermediate area lies between lubricating re quirements necessitating an extreme pressure lubricant and requirements that may be met satisfactorily with straight run lubricating oils. In this area of boundary or so-called thin film lubrication, the oil is required to have a high film strength but need not possess extreme pressure characteristics. Various compounds known in the art impart to a lubricant the properties necessary to meet the anti-wear requirements of this intermediate area of lubrication. Among these compounds are long-chain fatty acids, fatty oils and esters. Another additive of this nature is tricresyl phosphate which is recognized as an outstanding anti-wear agent.

According to the present invention it has been discovered that the addition of a small amount of acids obtained by oxidation of highly refined petroleum oils of naphthenic nature, such as white oils, imparts unusual and unexpected anti-wear properties to the lubricant in question. The oils from which the acids are derived should have an initial boiling point within the range of 450 to 700 F. and low viscosity, preferably between 34 and 160 SSU at 100 F., although the upper limit may be as high as 450 SSU at 100 F. The anti-wear eifect of the acids obtained by oxidation of these oils is superior to that of long-chain acids or esters used heretofore and is equivalent to the effect of tricresyl phosphate. The quantity of the acids added may vary from 0.01 to 5.0% by weight, based on the total composition, the preferred range being 0.1 to 1.5%.

The synthetic acids described above are obtained by the oxidation of mixturesof petroleum hydrocarbons, preferably of naphthenic nature and more specifically highly refined petroleum oils of the type of white oils. These oils are manufactured by treating a gas oil of naphthenic nature with fuming sulfuric acid. Following this treatment, the oil is passed to a sweetener, neutralized and washed. These white oils have a very high unsulfonatable content, of at least 90% and generally between 96 and 100%. A further description of white oils and their preparation is given in Science of Petroleum, vol. V, part III, pages 189-193 (1955).

The preferred method of producing the synthetic acids is by blowing these highly refined petroleum oils with oxygen or air at 210 F. to 390 F., preferably at about 300 F., until the desired degree of oxidation has taken place. As a rule, about 50 to 60 percent conversion makes for easy operation of the process. At this point the oxidized material may be topped to remove the unchanged hydrocarbon or if preferred, the whole material may be extracted with aqueous alkali or with concentrated ammonia. For easy operation, an alcohol may be added in amounts equal to the amount of water used in making the alkali or ammonia solution in order to render the salts formed more soluble. The unchanged hydrocarbon and non-acidic oxidation materials are removed by extraction with naphtha. On acidification of this aqueous solution with HCl, H2804 or other mineral acid, the acids are liberated in the form of oil.

In the tests listed below the synthetic acids used were prepared in the following fashion:

A highly acid-treated petroleum distillate, essentially naphthenic in nature, containing on the average about l224 carbon atoms per molecule and having a 450 -650 F. boiling range was prepared as follows:

Gas oil of naphthenic stock, having a viscosity of about 35 to 40 SSU at 100 F. was subjected to treatment with fuming sulfuric acid. The oil was agitated with the acid in five stages, a period of time being allowed for settling out the sludge between each stage. The total volume of acid added amounted to approximately 30%. Following the acid treatment, the oil was passed to a sweetener for the purpose of removing any S02 present. It was then neutralized with the aid of NazCOs in alcohol solution, the soaps thus formed were removed and the oil washed with water. After this wash, the oil was allowed to separate from the water, any remaining alcohol was steamed off and the oil was percolated through clay for final purification.

1200 g. of this oil was charged into a glass reactor equipped with a porcelain thimble for the introduction of oxygen and a trap and return condenser for condensing and separating the water formed during the reaction. Then While stirring, a rapid stream of oxygen was passed through the reaction mixture at 300 to 320 F. Once this reaction had started, the external heating was discontinued and the temperature was regulated merely by regulating the flow of oxygen. The heat of reaction was sufficient to maintain the temperature at the desired level.

The oxygen was continued until ml. of water were caught in the water trap. The oxidized material was topped under 1 mm. pressure to 275 F. metal bath temperature. The distillate consisted of 616 g. of amber colored oil which in turn consisted partly of unchanged hydrocarbon and partly of acids, esters, and other oxygenated products. The undistilled residue consisted of 514 g. of a viscous light red oil. Henceforth, this product shall be referred to as the topped oxidation product.

In the normal course of operation the distillate described above can be recycled until the whole material is oxidized.

The topped material referred to above was transferred into a separatory funnel and was treated with a mixture of 600 cc. of isopropyl alcohol and 600 cc. of concentrated ammonia. The mixture was thoroughly shaken, whereupon it was extracted several times with petroleum ether in order to remove unchanged white oil, and nonacidic oxidized products. Ether extracts were discarded, though these too can be recycled if desired.

The alcoholic-ammonia solution was treated on the steam bath for a short time in order to remove most of the-excess of ammonia. The solution was then treated Withan excess of hydrochloricacid. The liberated acids separated in the form of an oil.

The latter was extracted with ethyl ether. The extract was washed free of HCl with water and-.wasthen dried over sodium sulfate. On' removal of the ether, the acids were obtained as viscousred oil weighing-228 g. These were then distilled under 1 mm. pressure. 122 g. of the product distilled between 300390. F. of which about. 80% distilled at 300335 F. The undistilledf residue was discarded. The finalproduct is a mixture ofacids having molecular weightsin the range ofabout 400 to 500.

The anti-wear effect of theseacid's in lubricating. oils has been determined in a 4-ball wear-tester machineiwhich is well known in the art for evaluating lubricants. The data below illustrate the beneficialeffect of the acids of this invention in comparison with that of conventional anti-wear additives. The oil used Was a phenol extracted mid-continent crude distillate: with aviscosity of 56 SSU at 210 F.

Goefli'ient'of Frietion' Wear Scar,

mm. One Hour at 10 Kg. Load Oil Composition 10 Kg. Load 20 Kg. Load No additive +05% Acids from Naphthenlc White +05% Naphthenic Acid... +05% Tricresyl phosphate In addition to being an excellent anti-wear-agent, the acids of the present invention also possess desirable-rust inhibiting properties, as revealed by the ASTM'Rust Test 40 data listed below. The oil used in thesetests was a phenol extracted mid-continent crude distillate with a viscosity'of 43 SSU at 210 F.

ASTM TURBINE OIL RUST TEST (48- hours at 140 F. with distilled water) Oil Composition" Rust Test Results +01% Acids from NaphthenicWhite on; No Rustin- +0.05% Acids from Naphthenie White Oil. 'Do.

No Additive Heavy Busting.

These results are peculiar to acids obtaine'dfrom white oils of naphthenic nature. As indicated by the data' be low, it has been found that'acidsproduced by the'oxidation of isoparaffinic white oils are not goodrustinhibitors; The oil used was the same as that usedin the preceding tests.

ASTM TURBINE OIL RUST TEST (48 hours at 140 F. with distilled water) on Composition Rust Test Results +0.05% Acids from Isoparafiinic White Oil (M01. Wt. 296)-- Busting. +0.05% Acids from Isoparaflinic White Oil (M01. Wt. 328).. Do.

also be incorporated into the lubricant compositions to impart to them certain desirable characteristics as willbe understood by those skilled in the art. The acids may also be utilized in greases and other solid or semi-solid lubricants which contain major proportions of lubricating oil as lubricating agent Where improved anti-wear or antirust propertiesare desired. The thickeners employed in the formulation of such greases comprise; for example, alkali or alkaline earth metal soaps of high molecular weight saturated or unsaturated carboxylic acids, such as sodium or calcium stearate, hydroxy stearate, oleate, ricinoleate, etc. Inorganic grease thickeners may also be used, such as carbon black, silica'gel, b entonite, etc.

What is claimed is:

l. A lubricant composition comprising a major proportion of lubricating-oil and about 0.01% to 51% by weight, based on the total composition, sufiicient to improve the anti-wearand anti-rust properties of said lubricant, of free acids obtained by the oxidation of a naphthenic white oil having a-high unsulfonatable content, an initial boiling point within the range of about 450 to 700 F. and a viscosity at F. oflabout' 34 to 450 SSU obtained by treating a naphthenicoil with fuming sulfuric acid.

2. A lubricating oil composition comprising a major proportion of lubricating oil and about-0.1 to 15% by Weight, based on the total composition, sutficient to improve the anti-wear an'd'anti-rust properties of said lubricant, of free acids obtained by the oxidation of a naphthenic white oil-havingahigh unsulfonatable content, an initial boiling point within the range of about 450 to 700 F. and a viscosity at- 100 F. ofabout 34 to 450- SSU obtained by'treating a naphthenic oil with fuming sulfuric acid.

3. A composition as in claim 2 wherein the naphthenic white oil is essentially; free of aromatic compounds.

4. A composition as incla'im 2 whereinthe lubricating oil is a mineral oil.

5'. A lubricatinggrease comprising a-m'ajor proportion ofthe composition described in'claim Zanda grease forming proportion of a thickener.

6. A lubricant composition comprising a major proportion of lubricating oil and a minor proportion, sufiicient to improve the anti-wear and anti-rus't-pr'operties of said lubricant, of a mixture ofacids having molecular weights Within the range of'about 400 to 500 obtained by bubbling oxygen throughnaphthenic white oil, having a high unsulfonatable content, an initial boiling'point within the range of-about'450'to 700 F., and a viscosity at 100 F. of 'about'34 to 450 SSU obtained by treating a naphthenic oil with fuming sulfuric acid, recovering the oxidized material, extracting the'sapo'nifiable material from saidoxidized' matter with the aid of an alkaline material and acidifying the extracted 5 material by treatmenfwith a mineral acid. I

7. A compositionas in claim 2, wherein-the'said acids are obtained by bubbling oxygenthrough said white oil, until about 50'to 60% of's'aid whiteoilis oxidized, recovering the oxidized material by distillation, extracting the saponifiable mater ial from said oxidizedmatter with the aid of an alcohol and ammonia and acidi'fyingthe extracted material'by treatment with a miner'al acid.

References Cited in the file of this patent UNITED STATES PATENTS ER ENCEST 7 Motor OilsiandEngine Lubrication, by Georgi; Reinhold Pub. Co., New York-1950, pages 9.8and 99L Ind; and Eng; Chem Vol.48, No. 12, December. 1918; pages'2342l and 2343. 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL AND ABOUT 0.01% TO 5% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, SUFFICIENT TO IMPROVE THE ANTI-WEAR AND ANTI-RUST PROPERTIES OF SAID LUBRICANT, OF FREE ACIDS OBTAINED BY THE OXIDATION OF A NAPHTHENIC WHITE OIL HAVING A HIGH UNSULFONATABLE CONTENT, AN INITIAL BOILING POINT WITHIN THE RANGE OF ABOUT 450 TO 700* F. AND A VISCOSITY AT 100* F. OF ABOUT 34 TO 450 SSU OBTAINED BY TREATING A NAPHTHENIC OIL WITH FUMING SULFURIC ACID. 